Nineteen polychlorinated biphenyl (PCB) congeners, such as 2,2′,3,3′,6-pentachlorobiphenyl (PCB 84), display axial chirality because they form stable rotational isomers, or atropisomers, that are non-superimposable mirror images of each other. Although chiral PCBs undergo atropselective biotransformation and atropselectively alter biological processes, the absolute structure of only a few PCB atropisomers has been determined experimentally. To help close this knowledge gap, pure PCB 84 atropisomers were obtained by semi-preparative liquid chromatography with two serially connected Nucleodex β-PM columns. The absolute configuration of both atropisomers was determined by X-ray single-crystal diffraction. The PCB 84 atropisomer eluting first and second on the Nucleodex β-PM column correspond to (aR)-(−)-PCB 84 and (aS)-(+)-PCB 84, respectively. Enantioselective gas chromatographic analysis with the β-cyclodextrin-based CP-Chirasil-Dex CB gas chromatography column showed the same elution order as the Nucleodex β-PM column. Based on earlier reports, the atropisomers eluting first and second on the BGB-172 gas chromatography column are (aR)-(−)-PCB 84 and (aS)-(+)-PCB 84, respectively. An inversion of the elution order is observed on the Cyclosil-B gas chromatography and Cellulose-3 liquid chromatography columns. These results advance the interpretation of environmental and human biomonitoring as well as toxicological studies.
Digital Object Identifier (DOI)
This work was supported by grants ES05605, ES013661 and ES017425 from the National Institute of Environmental Health Sciences/National Institutes of Health. The X8 Proteum diffractometer was funded by the National Science Foundation (MRI CHE0319176), and by the University of Kentucky (cost share).
The online version of this article (doi: 10.1007/s11356-017-9259-z) contains supplementary material, which is available to authorized users.
Li, Xueshu; Parkin, Sean R.; and Lehmler, Hans-Joachim, "Absolute Configuration of 2,2',3,3',6-Pentachlorinatedbiphenyl (PCB 84) Atropisomers" (2018). Chemistry Faculty Publications. 156.